Oblique parts or surfaces

ABSTRACT

Various structures, such as microstructures and wall-like structures, can include parts or surfaces that are oblique. In some implementations, a cantilevered element includes a spring-like portion with a uniformly oblique surface or with another artifact of an oblique radiation technique. In some implementations, when a deflecting force is applied, a spring-like portion can provide deflection and spring force within required ranges. Various oblique radiation techniques can be used, such as radiation of a layer through a prism, and structures having spring-like portions with oblique radiation artifacts can be used in various applications, such as with downward or upward deflecting forces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/974,933, filed Oct. 27, 2004, now U.S. Pat. No. 7,771,803, the entirecontents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to techniques in whichstructures have oblique parts or surfaces. For example, microstructuresor walls may have parts that extend obliquely relative to a substrate'ssurface.

Various techniques have been developed for producing structures with oneor more dimensions smaller than 1 mm. In particular, some techniques forproducing such structures are referred to as “microfabrication.”Examples of microfabrication include various techniques for depositingmaterials such as sputter deposition, evaporation techniques, platingtechniques, spin coating, and other such techniques; techniques forpatterning materials, such as photolithography; techniques forpolishing, planarizing, or otherwise modifying exposed surfaces ofmaterials; and so forth.

Various types of structures with oblique parts have been proposed. Forexample, bent metal parts with oblique angles have been used inconnectors and for other purposes in electronic assemblies, sometimesbeing bonded to a printed circuit board or other substrate or structure,such as by soldering or gluing.

Also, spring contacts and other microfabricated structures have beenproposed in which parts extend obliquely from a surface. U.S. Pat. Nos.6,184,053 and 6,727,580, for example, describe spring contact elements,each with a base end, a contact end, and a central body portion. Thecontact end is offset horizontally and vertically from the base end. Theelements are fabricated by depositing at least one layer of metallicmaterial into openings defined in masking layers deposited on a surfaceof a substrate. Other techniques for spring contacts and similarstructures are described in U.S. Pat. Nos. 5,613,861; 6,528,350; and6,616,966 and U.S. Patent Application Pub. No. 2003/0199179-A1.

Previous techniques are limited, however, in their ability to produce awide variety of structures such as cantilevers or walls with obliqueparts or surfaces. It would therefore be advantageous to have additionaltechniques for structures with oblique parts or surfaces.

SUMMARY OF THE INVENTION

The invention provides various exemplary embodiments of methods,apparatus, and structures. In general, each embodiment involves aportion, section, or other part or a surface that can be characterizedas oblique.

These and other features and advantages of exemplary embodiments of theinvention are described below with reference to the accompanyingdrawings, in which like reference numerals refer to components that arealike or similar in structure or function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an array of microstructures with springcantilevers that include oblique parts.

FIG. 2 is a perspective view of another array of microstructures withspring cantilevers with oblique parts that include polymer walls.

FIG. 3 is a cross-sectional view of a preliminary stage in exemplarytechniques that fabricate microstructures with oblique parts, such asthose in FIGS. 1 and 2.

FIG. 4 is a cross-sectional view of a stage following that in FIG. 3.

FIG. 5 is a top view of the stage shown in FIG. 4.

FIG. 6 is a top view of a portion of a mask that could be used in thestage in FIG. 3.

FIG. 7 is a top view of a portion of an alternative mask that could beused in the stage in FIG. 3.

FIG. 8 is a schematic optical illustration of an exposure system thatcould be used in the stage in FIG. 3.

FIG. 9 is a schematic optical illustration of another exposure systemthat could be used in the stage in FIG. 3.

FIGS. 10-12 are successive cross-sectional views of stages followingthat in FIG. 4.

FIG. 13 is a top view of an exemplary implementation of the stage shownin FIG. 12.

FIG. 14 is a top view of a portion of a mask that could be used in thestage in FIG. 12.

FIG. 15 is a top view of an alternative exemplary implementation of thestage shown in FIG. 12, produced using a mask similar to that in FIG.14.

FIGS. 16 and 17 are successive cross-sectional views of stages followingthat in FIG. 12.

FIGS. 18 and 19 show two stages in an application of the microstructureshown in FIG. 17.

FIG. 20 shows another application of the microstructure shown in FIG.17.

FIG. 21 is a cross-sectional view of another application that couldemploy a microstructure like that shown in FIG. 4.

FIG. 22 shows ways in which the angle of illumination during the stageshown in FIG. 3 could be modified.

FIG. 23 shows a cross-sectional view of a stage that is an alternativeto the stage shown in FIG. 3.

FIG. 24 shows a cross-sectional view of a stage that is an alternativeto the stage shown in FIG. 4.

FIG. 25 shows a cross-sectional view of a stage that is an alternativeto the stage shown in FIG. 17, based on features of the stage in FIG.24.

FIG. 26 shows a perspective view of an apparatus in which obliquewall-like structures hold an object.

FIG. 27 shows a series of cross-sectional views along the line 27-27′ inFIG. 26, showing stages in fabricating wall-like structures.

FIG. 28 shows a cross-sectional view illustrating an alternative to thetechnique of FIG. 27.

FIG. 29 is an image showing v-shaped structures produced by thetechnique illustrated in FIG. 28.

FIG. 30 is a schematic top view of v-shaped structures as in FIG. 29holding objects inserted between them.

FIG. 31 is a schematic top view of apparatus in which two symmetricalwall-like structures have an end at which they are more spread apart topermit insertion of an object.

FIG. 32 shows a cross-sectional view of another exemplary implementationin which two wall-like structures hold an object in position.

FIG. 33 shows a cross-sectional view of yet another exemplaryimplementation in which two wall-like structures hold an object inposition.

FIG. 34 shows a cross-sectional view of another exemplary implementationin which one wall-like structure holds an object in position against asidewall.

FIG. 35 is a schematic top view of apparatus including structures as inFIG. 32 holding a capillary tube connected to a microchannel.

FIG. 36 is a perspective view of an apparatus in which obliquecylinder-like structures hold an object.

DETAILED DESCRIPTION

In the following detailed description, numeric ranges are provided forvarious aspects of the embodiments described. These recited ranges areto be treated as examples only, and are not intended to limit the scopeof the claims. In addition, a number of materials are identified assuitable for various facets of the embodiments. These recited materialsare to be treated as exemplary, and are not intended to limit the scopeof the claims.

In general, the structures, elements, and components described hereinare supported on a “support structure” or “support surface”, which termsare used herein to mean a structure or a structure's surface that cansupport other structures; more specifically, a support structure couldbe a “substrate”, used herein to mean a support structure on a surfaceof which other structures can be formed or attached by microfabricationor similar processes.

The surface of a substrate or other support surface is treated herein asproviding a directional orientation as follows: A direction away fromthe surface is “up” or “over”, while a direction toward the surface is“down” or “under”. The terms “upper” and “top” are typically applied tostructures, components, or surfaces disposed away from the surface,while “lower” or “underlying” are applied to structures, components, orsurfaces disposed toward the surface. In general, it should beunderstood that the above directional orientation is arbitrary and onlyfor ease of description, and that a support structure or substrate mayhave any appropriate orientation.

In addition, the term “oblique” is used herein to characterize anorientation that is neither parallel nor perpendicular to a referenceplane, typically a support surface. If a support surface is not planar,“obliqueness” is determined relative to an intersection region in whicha part or surface having a given orientation meets the support surfaceor would, if extended along the given orientation toward the supportsurface, meet the support surface. For example, if the intersectionregion is approximately planar, obliqueness can be determined relativeto a tangent or normal to the intersection region.

A component or element “extends obliquely” relative to a surface whenthe component or element extends in one or more directions that areneither parallel nor perpendicular to the surface or to the intersectionregion of the component or element with the surface. A part of astructure, a component, or an element that extends obliquely may bereferred to herein as an “oblique part”.

In some implementations, an oblique part may “extend obliquely away”,meaning that it extends in a direction that is neither parallel norperpendicular to a support surface or in a range of directions that doesnot include parallel or perpendicular to the support surface. Similarly,an oblique part may “extend obliquely along a length” from a partsupported on a surface to a free part or end, meaning that it extendsalong a length from the part supported on the surface to the free partor end and at no intermediate point along the length is its directionparallel or perpendicular to the surface.

A structure or component is “directly on” a surface when it is both overand in contact with the surface. A structure is “fabricated on” asurface when the structure was produced on or over the surface bymicrofabrication or similar processes. A structure or component is“attached” to another when the two have surfaces that contact each otherand the contacting surfaces are held together by more than meremechanical contact, such as by an adhesive, a thermal bond, or afastener, for example.

A process that produces a layer or other accumulation of material overor directly on a substrate's surface can be said to “deposit” thematerial, in contrast to processes that attach a part such as by forminga wire bond. A structure or component over which material is depositedand that has a shape that is followed by the deposited material issometimes referred to herein as a “mold”.

Some exemplary embodiments of the invention are “microstructures”, aterm used herein to mean a structure with a maximum dimension less than10 mm and with at least one outside dimension less than 1.0 mm. Forexample, a relatively large microstructure could be 5.0 mm high and 0.5mm wide. In general, no minimum dimension is specified formicrostructures, but specific materials, functional characteristics, orother constraints may require that a microstructure have at least someappropriate minimum dimension.

FIG. 1 shows array 100 of microstructures on substrate 102. Array 100illustratively includes six substantially identical microstructures allsupported on surface 104 of substrate 102. Each of the microstructuresis an example of a “cantilevered element”, which is used herein to meanan element that is supported only on one part, that extends from thesupported part to a free part, and that has at least one outer dimensionsubstantially orthogonal to but smaller than the element's length fromthe supported part to the free part. For example, the substantiallyorthogonal, smaller dimension of a tubular cantilevered element could beits diameter; if a cantilevered element is a wall, its thickness, andpossibly also its width, could be substantially orthogonal and smallerthan its length. In FIG. 1, each microstructure has both a thickness anda width that are less than the length from where it is supported onsurface 104 to its free part. The ratio of length to thickness isillustratively greater than 20, and the ratio of length to width isillustratively about 4, but these are merely exemplary, and variousother ratios could be successfully implemented.

Representative microstructure 110 includes three parts, each of which issubstantially planar. As used herein, a surface is “substantiallyplanar” if it lies entirely or almost entirely in a plane. Similarly, apart or portion of a structure is “substantially planar” if it has twosubstantially planar surfaces that are substantially parallel and areseparated by a distance or “thickness” that is significantly smallerthan other dimensions of the part or portion. For example, part of amicrostructure would be substantially planar if its thickness wereapproximately 10% or less of its largest dimension. A part of a largercantilevered element fabricated on a substrate, such as a wall, would besubstantially planar if its thickness were approximately 10% or less ofits length from its base to its free part.

First part 112 is supported on surface 104, providing an example of abase of a cantilevered element. The term “base” is typically used hereinto mean the part on which a cantilevered element is supported, and thebase is typically directly on or over a support surface, as in FIG. 1.

Second part 114 connects or joins to first part 112 at joint 116. Thirdpart 118 is connected or joined to second part 114 at the end oppositefirst part 112. In array 100, third part 118 provides an example of afree part of a cantilevered element, but a free part could merely be anend of an obliquely extending part or could have any other appropriatestructure or shape, some examples of which are described below. Thirdpart 118 is substantially parallel to surface 104 when microstructure110 is unstressed, and therefore does not extend obliquely relative tosurface 104.

As shown, second part 114 extends obliquely away from surface 104. Moreparticularly, second part 114 extends obliquely in relation to surface104 and in relation to a central plane of first part 112, which issubstantially parallel to surface 104 and therefore perpendicular to thenormal to surface 104.

Second part 114 and most other oblique parts, components, and otherelements described below have both an “upper surface,” meaning anupward-facing portion of surface, and also a “lower surface,” meaning adownward-facing portion of surface. In general, an oblique element'supper and a lower surface, rather than being planar as in FIG. 1, couldinstead be curved (as with a cylinder, for example) or polygonal (aswith a hexagon, for example). In addition, an oblique element could havesurfaces facing laterally rather than upward or downward, i.e. sidesurfaces perpendicular to the support surface. It is also within thescope of the invention to provide an oblique element with either anupper surface and an opposite surface that is perpendicular to thesubstrate rather than facing downward or with a lower surface and anopposite surface that is perpendicular to the surface rather than facingupward.

A specific feature of second part 114 is its substantially planar lowersurface, described in greater detail below, also extending obliquelyaway from surface 104. As used herein, a substantially planar surface orpart of a surface is “oblique” in relation to a support surface if thesubstantially planar surface or part extends in a direction that isneither parallel nor perpendicular to the support surface.

An oblique substantially planar surface is one example of “uniformlyoblique” surfaces. As used herein, a surface or part of surface is“uniformly oblique” if the tangents at all points of the surface or partof surface that provide the shortest distances to any relevant referenceplane all extend in approximately the same oblique direction, subject toprocess limitations as described below. In addition to obliquesubstantially planar surfaces, various other surfaces or parts ofsurfaces would be uniformly oblique, including upper and lower surfacesof oblique walls of various curved or irregular shapes.

The presence of a uniformly oblique surface is a significant artifact ofcertain advantageous techniques for fabricating structures on surfaces,referred to herein as “oblique radiation techniques” because they arecharacterized by application of oblique radiation to a layer ofmaterial. If the material is photoresist, oblique radiation atappropriate wavelengths exposes it, allowing removal either of unexposedor exposed regions if the photoresist is negative or positive,respectively. For a wider range of materials, oblique laser radiationcan be used to perform ablation, removing material in the laserradiation's path. Oblique radiation techniques generally depend on thedepth of the layer to which oblique radiation is applied; for example,because photoresist and other polymers act to block light by absorption,the depth of effective photo-exposure is limited, such as to 2-3 mm orless for SU-8 layers.

A cantilevered element could be produced in various ways using obliqueradiation techniques, some of which are described below. For example, apolymer cantilevered element could be produced by exposing anddeveloping a negative photoresist such as SU-8 or by performing laserablation on a layer of polymer material. A polymer plating mold orinsert mold could be produced by either of those techniques, and couldthen be used to produce a cantilevered element by a plating or embossingoperation, respectively.

When produced in any of these ways, a resulting cantilevered elementwill typically have at least one “oblique radiation artifact”, meaningan artifact of the oblique radiation process used to produce it. Forexample, when a cantilevered element is produced through a process thatincludes oblique radiation techniques, it may have a section with auniformly oblique surface, and the section may extend along most of thelength from the cantilevered element's base to its free end. Similarly,oblique radiation techniques can produce a polymer plating mold with auniformly oblique upper surface, in which case a cantilevered elementplated on the mold usually has a uniformly oblique lower surface alongmost of its length. Also, oblique radiation techniques can produce aninsert mold with uniformly oblique upper and lower surfaces, in whichcase a cantilevered element embossed by the mold usually has uniformlyoblique upper and lower surfaces along most of its length.

Uniformly oblique surfaces are not the only oblique radiation artifacts.For example, a component produced by an oblique radiation processtypically has a cross-section that is approximately symmetrical about anoblique central axis, even if unintended material or process variationspreclude formation of uniformly oblique surfaces. Variations that couldhave this effect include warping of a polymer wall due to softening,changes in shape due to light reflection from a substrate, and so forth.Furthermore, an oblique radiation process may be intentionally used in amanner that precludes uniformly oblique surfaces but leaves otheroblique radiation artifacts. For example, using a circular mask patternand rotating angle of exposure around an oblique axis would produce anoblique conical structure.

As noted above, the definition of “uniformly oblique” allows for processlimitations. For example, if a layer of negative photoresist such asSU-8 is exposed with an oblique radiation technique and then developed,the resulting polymer component's profile will be slightly reentrant ortapered due to attenuation of radiation within the photoresist; asurface of the polymer component will nonetheless be “uniformly oblique”within the above definition if it would have been uniformly obliquewithout the slight reentrance or tapering due to process limitations.Other process limitations result in other slight variations from uniformobliqueness, some of which are mentioned herein, but the resultingsurfaces or parts are nevertheless “uniformly oblique” within the abovedefinition.

In the example in FIG. 1, second part 114 and surface 104 define anoblique angle with joint 116 at its vertex. Cantilevered elementsconnected or supported in various other ways are within the scope of theinvention. Cantilevered elements with curved portions, for example aredescribed below in relation to FIGS. 24 and 25. FIGS. 2, 4, 21, 24, 26,27, and 29-36 illustrate variations in which at least one polymer partis supported on a base end.

Each of the microstructures in FIG. 1 also has a “spring-like portion”,meaning a portion that returns elastically to substantially its originalshape when released after being deformed; this elastic behavior is amaterials property. A spring-like portion that includes some or all of acantilevered element may also have plastic deformation, especially ifsubject to an extraordinary stress, but across some useful range ofstresses its deformation is substantially elastic and can becharacterized by an appropriate spring constant. In the ideal case, theproduct of a spring's spring constant with the distance it is deflectedis proportional to the spring force, i.e. force exerted by the spring inresponse to force causing its deflection, referred to herein as“deflecting force”. A spring-like portion or the like is referred toherein as “undeflected” when it is subject to approximately zerodeflecting force.

Specifically, when deflecting force toward or away from surface 104 isapplied to third part 118 or otherwise to a point along the length ofmicrostructure 110, its spring-like portion is elastically deformed inaccordance with its spring constant. When released, the spring-likeportion returns toward its initial shape. Ideally, the spring-likeportion returns to its initial unstressed shape, although in practicalimplementations, some plastic deformation may occur.

The spring-like portion of each microstructure in FIG. 1 has “length”,meaning distance it extends from its base to its free part, and also has“effective length”, meaning distance it extends from its base to whereit effectively receives deflecting force in use; for a given instance ofdeflection, the effective length extends to a position around whichdeflecting force is balanced, and typically does not exceed the length.Each spring-like portion also has “thickness”, meaning distance betweenits upper and lower surfaces. Each spring-like portion also has “width”,meaning lateral distance across its upper and lower surfaces in adirection generally perpendicular to length.

While each of these dimensions may have more than one value for a givenspring-like portion, all the values of a dimension may share a givencharacteristic. In exemplary implementations of the invention describedherein, the thickness of each spring-like portion is less than itslength, meaning that any measurement of its thickness is less than anymeasurement of its length. In many implementations, alength-to-thickness ratio of 3 or more is sufficient for a spring-likeportion to be appropriately deflected while providing substantial springforce, given a suitable material. In specific implementations, aspring-like portion's thickness might not exceed 10% of its length,similarly meaning that any measurement of its thickness is no greaterthan 10% of any measurement of its length. A length-to-thickness ratioof 10 or higher is likely to allow much greater possible deflection thana ratio of 3 as discussed above, but will not provide as much springforce. Where the effective length is shorter than the length, similarconsiderations apply to the ratio of effective length to thickness.

To be useful in a practical application, a cantilevered element'sspring-like portion must typically meet certain requirements appropriateto the application. Specifically, it may be required to have deflectionand spring force in certain ranges in response to deflecting force thatoccurs in the application, and such ranges are referred to herein as“required ranges”. Several factors affect a spring-like portion'sdeflection and spring force, including its material structure, itseffective length, its thickness, and its width.

In the example of FIG. 1, each microstructure can be used or applied asa “spring cantilever”, meaning a cantilever that behaves like a spring.In other words, a spring cantilever has a projecting member supported atonly one end, and the projecting member is elastic in that it returns tosubstantially its original shape when released after being deflected.

Spring cantilevers can be used, for example, in spring contact arrays,described below in relation to FIGS. 18 and 19, or in surface detectionarrays, described below in relation to FIG. 20. In these applications,the required ranges of deflection and spring force are based on thenecessary movement of the spring cantilever in response to deflectingforce and the responsive force necessary to maintain electrical ormechanical contact. For spring contact or surface detection arrays, therequired range of deflection may also be based on the movement necessaryto ensure that all elements in the array are making good contact at alltimes.

As described below in relation to FIG. 21, a spring cantilever can alsobe used to hold an object in position under it. In this and similarapplications, the required ranges of deflection and spring force arebased on the movement necessary to allow insertion (and possiblyremoval) of the object and the responsive force necessary to hold theobject after insertion.

Deflection and spring force within required ranges can be obtained invarious ways. For example, proportions of effective length, thickness,and width can be tested experimentally until satisfactory proportionsare obtained for a given material structure.

FIG. 2 illustrates an alternative exemplary implementation in which apolymer wall affects a cantilevered element's deformationcharacteristics such as deflection and spring force. As used herein,“polymer” refers to any material that includes one or more compoundsformed by polymerization and that has properties resulting from presenceof those compounds. Also, as used herein, “wall” means a cantileveredelement or a component with upper and lower surfaces that areapproximately parallel and with length and width that are both greaterthan thickness.

In FIG. 2, array 130 again includes a number of microstructuressupported on substrate 102. Representative microstructure 140 includesfirst part 112, second part 114, joint 116, and third part 118 asdescribed in relation to FIG. 1. In addition, microstructure 140includes polymer wall 142, with an oblique upper surface 144 supportingsecond part 114 and with a horizontal surface 146 supporting third part118. In this implementation, polymer wall 142 can be sufficiently thinto be flexible and elastically deformable to an extent, while first part112, second part 114, and third part 118 can be an electricallyconductive material, providing an electrically conductive path fromthird part 118 to circuitry supported on substrate 102. When the springcantilever is distorted, polymer wall 142 flexes; second part 114 andthird part 118 remain on surfaces 144 and 146, respectively. The ratioof length to thickness for microstructure 140 is illustratively about 4,and the ratio of length to width is illustratively about 2, which areagain merely exemplary.

Polymer wall 142, together with surface 104 of substrate 102, provides amold or form that can be used in producing other components ofmicrostructure 140. It would be possible to form the parts in anappropriate sequence. As described in greater detail below, however,first part 112, second part 114, joint 116, third part 118, and theconnection between second part 114 and third part 118 can all beconcurrently deposited using plating or other deposition techniques andpatterned using photolithographic techniques. Specifically, first part112 can be deposited on surface 104 or over other layered structuressuch as contacts and other electrical circuitry on surface 104. Secondpart 114 can be deposited on upper oblique surface 144, third part 118on horizontal surface 146, joint 116 at the edge where surfaces 134 and144 meet, and a similar joint between part 114 and part 118 at the edgewhere surfaces 144 and 146 meet.

FIGS. 1 and 2 illustrate microstructures with surfaces that includeuniformly oblique sections and, more specifically, substantially planarsections. Examples of uniformly oblique sections of surfaces include thelower surface of second part 114 in both figures and upper surface 144in FIG. 2, all of which extend along approximately the entire length ofa cantilevered element's spring-like portion from its base on a supportsurface 104 to its free part. In some other implementations, a uniformlyoblique section of a surface extends approximately 60%, 75%, or 90% of aspring-like portion's entire length, and other variations are possible.

FIG. 3 illustrates a preliminary stage in producing a microstructuresuch as microstructure 110 in FIG. 1 or microstructure 140 in FIG. 2.Substrate 102 can, for example, be a silicon wafer polished on one sideor a glass substrate. Prior to the stage shown in FIG. 3, photoresistlayer 160 has been deposited on surface 104 of substrate 102. Layer 160can, for example, be formed of an appropriate photopolymer such as SU-8from MicroChem Inc. or DiaPlate from HiTech Photopolymere AG, or anotherphotoresist that can be used to produce relatively tall microstructureswith high aspect ratios, i.e. high ratios of height to width. SU-8structures above 1.0 mm in height are feasible and DiaPlate structuresup to 0.5 mm in height have been reported. Layer 160 can be deposited toan appropriate thickness, such as between tens and a few thousands ofmicrons.

Because SU-8, for example, is a negative photoresist, regions of SU-8that are exposed to ultraviolet (UV) light are not removed duringsubsequent development and removal of unexposed regions. A maskingstructure 162 placed over photoresist layer 160 illustratively includesa single slot or opening through which light can be projected from asource onto layer 160. If the light is received at the angle α₁ from thenormal, an exposed portion of layer 160 will extend at an oblique angleα₂ that is a function of α₁, as described below. Angle α₁ should besufficiently great that errors will not result in vertical structures.An α₁ angle no less than approximately 10° should satisfy thisconstraint, and larger values may be desirable for many applications. Asdescribed in relation to FIG. 22 below, angles up to approximately 70°should be obtainable.

Mask 162 can be a conventional glass photomask, directly in contact withlayer 160 or with an air gap between the mask and layer 160 as in theproximity mode of exposure. Various other masking schemes could be used,including some in which a glass plate is not present, or, if substrate102 is transparent, backside exposure through a suitable mask can beused. Of course, a positive photoresist (such as ma-P 100 fromMicroResist Technology or AZ 9200, AZP4000, AZ PLP 100XT from Clariantand others) may also be used. With the presently available negativeresists, particularly SU-8, higher structures with higher aspect ratiosare achievable than with positive resists. In the case of positivephotoresist, the exposed area is dissolved during the developmentprocess and the mask pattern would be reversed.

After exposure as illustrated in FIG. 3, and after further processing,including development of layer 160 and removal of nonexposedphotoresist, the structure shown in FIG. 4 is obtained. In addition tophotoresist wall 170 extending at an oblique angle α₂ from the normal,surface 104 of substrate 102 supports a conductive contact 172, whichcan be formed using microfabrication processes before or afterphotoresist wall 170. FIG. 5 shows a top view of the structure in FIG.4, illustrating the shapes of upper oblique surface 174 and horizontalsurface 176 of photoresist wall 170.

Photoresist wall 170, by itself, can have a thickness that allows it tofunction as a spring cantilever or spring-like portion of a cantileveredelement, with its base end supported on surface 104 and with horizontalsurface 176 at its free part. An exemplary thickness is 10 μm, but, ingeneral, the spring constant of a rectangular cantilever is proportionalto (width×thickness³/length³); therefore, as wall 170 is longer, itsthickness could be greater to maintain the same spring constant. Uppersurface 174 can be substantially planar and can extend the entire lengthif the production process is performed as described above using asuitable mask.

If SU-8 is used to produce photoresist wall 170, the well-known mainsteps for SU-8 baking and processing can be followed, but withappropriate changes for specific dimensions of wall 170. For example, ifwall 170 is produced from a relatively thick layer of SU-8, longerexposure times, higher baking temperatures, and longer baking times canbe used to obtain a polymer wall of suitable flexibility.

Mask portion 180 in FIG. 6 includes an array of rectangular slots oropenings that would produce an array of microstructures like photoresistwall 170 in FIGS. 4 and 5, with substantially planar upper and lowersurfaces. Mask portion 182 in FIG. 7 shows an alternative shape foropenings that would result in walls with better mechanical stability atsmall wall-thicknesses, with a substantially planar upper surface butwith the lower surface being U-shaped. Masks such as those illustratedin FIGS. 6 and 7 and various other suitable masks could be used eitherfor frontside or backside exposure of photoresist layer 160, assuming atransparent substrate material is used.

Structures similar to FIGS. 4 and 5 could also be produced using variousother exposure techniques, such as using X-rays to expose a polymer suchas polymethyl methacrylate (PMMA) or using oblique laser direct exposureof photoresist. Furthermore, such structures could be produced byoblique laser ablation of a polymer. The structures could also beproduced by an embossing or molding technique in which an insert moldhas an oblique pattern produced by any suitable exposure technique, asdiscussed in relation to FIG. 23, below.

FIGS. 8 and 9 show exposure systems 200 and 210, either of which can beused in the stage illustrated in FIG. 3 or to produce an insert mold.Unlike conventional UV exposure systems, which are engineered forexposure perpendicular to a substrate, exposure systems 200 and 210expose a photoresist layer at an angle other than perpendicular.

Exposure system 200 is a very simple system with light source 202 andcollimator 204. Collimated light from collimator 204 reaches waferassembly 206, which can include substrate 102, photoresist layer 160,and mask structure 162 as shown in FIG. 3. As shown, the central planeof wafer assembly 206 is tilted in relation to the wave plane of thecollimated light by the angle α₁.

In exposure system 210, light source 202 and collimator 204 can beimplemented as in exposure system 200. In addition, aperture 212provides a small beam width for light reaching wafer assembly 206. Waferassembly 206 is mounted on a speed-controlled movable support 214 thatmoves relative to a stationary support 216. Stationary support 216 is inturn mounted on table 218 at an angle of α₁. In comparison with system200, system 210 eliminates exposure non-uniformity due to differences indistance between light source 202 and the surface of wafer assembly 206.Exposure system 210 also allows scaling of the exposure process tolarge-area substrates more easily.

Various other techniques could be used with these and other exposuresystems. See, for example, Han, M. H., Lee, W. S., Lee, S.-K., and Lee,S. S., “Fabrication of 3D Microstructures with Single uv LithographyStep”, J. of Semiconductor Technology and Science, Vol. 2, No. 4,December, 2002, pp. 268-272, incorporated herein by reference.

FIG. 10 shows a stage following the stage in FIG. 4, showing how wall170 functions as a mold. Seed layer 230 is illustratively deposited overthe entire surface of the structure; in some techniques, wall 170 mayhave a shadowing effect, in which case surfaces under wall 170 would notbe covered by seed layer 230. Seed layer 230 can be a thin layer of anappropriate metal, metal alloy, or other seed material on which materialcan be deposited by plating, such as by electroless plating,electroplating, or other electrodeposition. For example, seed layer 230could be a thin sputtered layer of titanium followed by gold (Ti/Au)with a total thickness between 50-100 nm or a thin layer of copper ornickel of similar thickness.

FIG. 11 shows a following stage in which thin photoresist layer 232 isdeposited over seed layer 230. Photoresist layer 232 must be suitablefor the high topography of the structure. For example, photoresist layer232 could be an electrodeposited photoresist such as an Eagle resistfrom Shipley Ronal or a spray coated photoresist.

Photoresist layer 232 is exposed through a suitable photomask definingthe shape of the microstructure to be produced. After development, thepart of layer 232 where the microstructure is to be deposited is removedto expose seed layer 230, as shown in the stage in FIG. 12. Because ofthe upward projection of cantilever-like photoresist wall 170,photolithography may vary in accuracy, with higher accuracy near the topof wall 170 than at the surface 104 of substrate 102, depending on thetotal distance between the photomask and the substrate and on thecollimation of the light source. To reduce reflections from obliquephotoresist walls, linearly polarized light may be used.

FIG. 13 shows an exemplary pattern for photoresist layer 232 in FIG. 12,for an implementation to produce a single microstructure. In FIG. 13,photoresist pattern 240 has a rectangular opening over contact 172,oblique upper surface 174, and horizontal surface 176. The rectangularopening could be used to produce a rectangular microstructure.

FIG. 14 shows portion 242 of a mask that could be used to producemicrostructures with shapes as in FIGS. 1 and 2. FIG. 15 is similar toFIG. 13, but shows photoresist pattern 244, in which the opening tapersbetween contact 172 and horizontal surface 176 due to use of a masksimilar to portion 242 in FIG. 14, producing a tip similar to third part118 in FIGS. 1 and 2. The mask portion 242 could be moved leftward inrelation to substrate surface 104 in order to obtain a tip without ahorizontal part; in other words, second part 114 in FIGS. 1 and 2 couldcome to a point rather than being connected to a third part parallel tosurface 104.

FIG. 16 shows a stage that follows deposition of material upon exposedportions of seed layer 230 in FIG. 12. This deposition could be done invarious ways. In particular, electroplating or electroless plating couldsuitably produce structure 260 with any appropriate combination ofmetals such as nickel, nickel phosphorus, copper, and gold, plated inconsecutive layers to a total thickness of 1-10 μm or more. Structure260 could also be produced by coating or plating with a solder materialsuch as lead-tin (PbSn) or with a magnetic material such as NiFe. Theshape of structure 260 will depend, of course, on the photoresistpattern, which may be as in either of FIG. 13 or 15 or any otherappropriate pattern.

If the material for structure 260 is deposited by a method such assputter coating or evaporation, then the patterning of structure 260could be done by a lift-off technique (in this case the deposit onphotoresist layer 232 could be “lifted off” when dissolving thephotoresist) or by etching of the deposit in the unwanted areas (in thiscase the shape of structure 260 would have to be protected by a layer ofpatterned photoresist). In these techniques, seed layer 230 would not benecessary. Various other materials could be deposited, including, forexample, materials that are hard to plate, such as aluminum or metaloxides such as titanium dioxide, vanadium oxide, and so forth.

After the stage in FIG. 16, the remaining part of photoresist layer 232can be stripped away with conventional techniques. Then seed layer 230can be etched away wherever it is exposed by removal of photoresistlayer 232. This will leave a structure like microstructure 140 in FIG.2. Then, if desired, photoresist wall 170 can be removed using anappropriate etchant, solvent, or a plasma process. This will producemicrostructure 270, shown in the stage in FIG. 17. Because of itsspring-like properties, microstructure 270 may be referred to as a“microspring.” With the illustrated dimensions, microstructure 270 has asubstantially planar lower surface that extends approximately 90% of thelength from surface 104 to the top surface of the free part; it may bepossible to obtain a substantially planar surface that is nearly 100% ofthe length, such as with a length of 100 μm and a thickness of 1-5 μm.

Microstructure 270 and similar structures produced as described abovecan be used in various applications in which spring-like, resilient,elastic, or bendable microstructures are useful. In particular, a highdensity array of such microstructures can be useful in a probing orpackaging application, such as for high-density probe contacts as inprobe cards, for microchip to printed circuit board interconnects, formicroscopic surface sensing, or for surface-based data storage. Incomparison with some previous techniques, microstructure 270 does notrequire stress engineering to move it out of the plane of its supportstructure. Also, the surface area required for fabrication of each suchmicrostructure in an array is very small, and not significantly greaterthan its projection onto the surface on which it is fabricated, allowingdenser packing within an array than some previous techniques. The abovetechnique for producing microstructures can be described as aninherently additive three-dimensional process, in contrast withprocesses that map structures from two-dimensions to three-dimensionsand therefore require more surface area for fabrication.

FIGS. 18 and 19 illustrate application of microstructure 270 to providea contact pin. In FIG. 18, microstructure 270 is positioned belowsubstrate 280. Contact 282 on surface 284 of substrate 280 is positionedabove microstructure 270. As indicated by the black arrow, substrate 280is moving toward substrate 102. FIG. 19 shows that mechanical (andtherefore electrical) contact has been made between contact 282 andmicrostructure 270. As a result of deforming force or stress exerted bycontact 282 on the upper surface of microstructure 270, microstructure270 is deflected so that its position is responsive to the position ofcontact 282. If plated structure 260 is conductive, microstructure 270will provide a conductive path between contacts 172 and 282. This makesit possible to connect circuitry on substrates 102 and 280.

As suggested in FIG. 19, the effect of the deforming force or stress isto change the shape of the spring cantilever of microstructure 270. Nosubstantial change in shape occurs in the free part, but some curvatureoccurs in the area of the second part midway between the free part andthe first part. The spring cantilever resiliently resists the deformingforce or stress, ensuring that a good electrical connection ismaintained where the third part of microstructure 270 is touchingcontact 282. Alternatively, a bump of solderable material such aslead-tin on the third part of microstructure 270 could be used to makepermanent electrical contact once initial contact is made.

FIG. 20 illustrates another application of microstructure 270,applicable to tips used in an atomic force microscope (AFM), a scanningtunneling microscope (STM), in AFM/STM data storage, or in otherapplications in which surface features are detected. Microstructure 270has an additional tip 290 which could be a deposited nanowire, adeposited tungsten tip, a deposited diamond grain, or other appropriatestructure; various techniques for providing tip structures aredescribed, for example, in U.S. Patent Application Pub. No.2003/0199179-A1 and in Baselt, D., “Atomic force microscopy—Measuringintermolecular interaction forces”, published at the Web sitestm2.nrl.navy.mil/how-afm/how-afm.html, both of which are incorporatedherein by reference.

In use, sample 292 is moved relative to substrate 102, so that tip 290makes contact (or is in close contact, such as in the non-contact AFMmode) with surface 294 of sample 292; this contact is maintained byspring force. When microstructure 270 is deflected in the mannersuggested by the phantom lines in FIG. 19, its position responds to theposition at surface 294. Therefore, a laser beam from laser source 296is reflected at a slightly different angle by seed layer 230 on thelower oblique surface of microstructure 270. As a result, detector 298detects the laser beam at a slightly different position, and provides anappropriate signal indicating the change in position and thereforeproviding information about features of the surface 294 of sample 292.

In the applications in FIGS. 18-20, downward deflecting force is appliedto each spring cantilever in an array. In response, each springcantilever's free part moves to a position resulting from deflectionbut, due to its spring force, maintains contact with the object orsurface providing deflecting force. In these applications employingarrays, it is also important that each spring cantilever's deflection besufficient that all spring cantilevers can be deflected despite anydifference in their heights.

A similar application of microstructure 270 is in the field of sensorsand actuators. If the structure 270 contains magnetic materials, thestructure may deflect in the presence of a magnetic field. Thisdeflection may be detected in a way similar to the one shown in FIG. 20employing laser beams. In this way, the structure 270 would be adetector for magnetic fields. The deflection of the structure 270 inmagnetic fields (when containing magnetic materials) may also be usedfor actuator applications. For example, if microstructure 270 were bothmagnetic and electrically conductive, a magnetic field could deflect itin a way to open or close a contact such as in a microswitch. Ormagnetic arrays of such microstructures may be applied to ciliaryactuation as described in Suh, J. W., Darling, R. B., Böhringer, K.-F.,Donald, B. R., Baltes, H., and Kovacs, G. T. A., “CMOS IntegratedCiliary Actuation Array as a General-Purpose Micromanipulation Tool forSmall Objects,” J. of Microelectromechanical Systems, Vol. 8, No. 4,December 1999, pp. 483-496.

FIG. 21 illustrates another application, in which microstructure 170 isoptionally formed on alignment block 300 or could be formed directly onsurface 104. Another alignment block 302 is formed in the same layer asblock 300. Microstructure 170 and blocks 300 and 302 are positioned sothat object 304, which could be an optical fiber, a capillary tube, aconductive wire, or another such approximately round object, is held inplace by the sidewalls of blocks 300 and 302 (or, if block 300 isomitted, by the sidewall of block 302 alone) after being laterallyinserted from the right in FIG. 21. During insertion, object 304 appliesdeflecting force away from surface 104 to the lower surface ofmicrostructure 170, but the deflection is sufficient to allow insertion.As a result of insertion, some curvature occurs in the portion ofmicrostructure 170 between block 300 and the point of contact withobject 304. After insertion, the spring force is sufficient to holdobject 304 in place.

As described below in relation to FIGS. 26-36, various otherarrangements could be used in similar applications, such as arrangementswith two opposing microstructures or without alignment blocks as shownand arrangements with microstructures extending in length across surface104. Microstructure 170 could have a deposited layer on it as shown inFIG. 2, and other implementations could be used, such as those in FIGS.1 and 17. Because of the clip-like nature of this application, it isreferred to as a “microclip.”

FIG. 22 illustrates in more detail how a desired oblique angle can beobtained during the stage illustrated in FIG. 3. As shown, light beam310 is incident upon masking structure 162, with glass plate 164, opaqueregion 166, and transparent region 168 filled with air or anindex-matching fluid. The angle of incidence is θ_(i) from the normal,resulting in a reflected beam 312, at an equal and opposite angle θ_(r)from the normal. In addition, transmitted light beam 314 travels throughglass plate 164 at an angle θ_(t) to the normal, and θ_(t) can becalculated from θ_(i) in accordance with Snell's Law.

Transmitted beam 314, in turn, is similarly divided at the surfacebetween glass plate 164 and transparent region 160. The resultingtransmitted beam is again divided between reflected beam 316 andtransmitted beam 318 at the surface between mask structure 162 andphotoresist layer 160. Reflected beam 316 is at an angle θ_(r2) from thenormal and transmitted beam 318 is at an angle θ_(t2) from the normal.

In the arrangement shown in FIG. 22, if we neglect the effect oftransparent region 168, a theoretical upper limit for the angle θ_(t2)can be calculated using the maximum incidence angle θ_(i) of 90° and therefractive indices of air (n_(air)=1), glass (n_(glass)=1.5), and SU-8(n_(su-8)=1.6):n _(air)·sin θ_(i) =n _(glass)·sin θ_(t)→θ_(t)=41.8°;n _(glass)·sin θ_(t) =n _(su-8)·sin θ_(t2)→θ_(t2)=38.7°.

Although this maximum angle for obliqueness of photoresist wallscompares favorably to the side wall angle that can be achieved in othermicrofabrication methods (such as anisotropic etching of silicon, i.e.,35.3°), FIG. 22 also illustrates another technique for obtaining higherangles of obliqueness.

As shown at right in FIG. 22, prism 330 can be used to achieve a greaterexposure angle for photoresist layer 160. Prism 330 can be opticallymatched to glass plate 164, and an appropriate index matching fluid maybe used at the surface between prism 330 and glass plate 164 to achieveoptimal optical index matching across the interface. In this case, withincident light beam 332 arriving at an angle θ_(i)′ from the normal, andwith transmitted light beam 334 continuing at an angle θ_(t)′ from thenormal, the theoretical upper limit for θ_(t)′, calculated in the samemanner as above, increases to 69.6°, because the only significantrefraction occurs at the interface between structure 162 and photoresistlayer 160. In other words, angles as great as approximately 70° could beobtained with this technique.

In either approach, with or without prism 330, reflections off thesubstrate or at other surfaces may be a problem. This problem may bealleviated by using antireflection coatings, polarized light, or otherappropriate techniques. More generally, various other modifications inthe arrangements illustrated in FIGS. 3, 8, 9, and 22 may be made toobtain a desired angle of exposure in photoresist layer 160. Forexample, laser direct exposure at an oblique angle could be performed asdescribed at the Web site people.bu.edu/xinz/pdf/MRS2003_fall-grace.pdf.

FIGS. 23-25 illustrate other modifications in the process of producingwall 170 and microstructure 270. As shown in FIG. 17, the joint betweenthe first and second parts of microstructure 270 is the vertex of anangle. An angular joint as in FIG. 17 concentrates stress when adistorting force or stress is applied to the second part of themicrostructure. As a result, cracking may occur at the connectionregion, and the microstructure may fail. In general, however, a springcantilever's connection to a base can have any appropriate shape andother shapes may reduce risk of failure.

In FIG. 23, insert mold 340 has been used to form polymer wall 342 froma layer of polymer material by a molding or embossing technique similarto the one described in Madou, M., Fundamentals of Microfabrication,Boca Raton, CRC Press, 1997, pp. 301-302. Insert mold 340 could beproduced as described above in relation to FIGS. 3 and 4, using obliquephotoresist exposure, and could be applied and removed at an appropriateangle. To obtain curved edges, appropriate additional operations such asthermal reflow or plasma etching could be performed on the insert moldbefore insertion. After insert mold 340 is removed, reactive ion etchingcould be performed to remove polymer material if appropriate.

In FIG. 24, polymer wall 342 includes a ramp section 350 at its base,where the upper surface of polymer wall 342 is curved rather thanplanar. Ramp section 350 extends from substantially planar section 352of the upper surface to surface 104 of substrate 102. A curved partsimilar to ramp section 350 could also be produced from photoresist wall170 in FIG. 4 by filleting in any of a number of ways, including partialreflow or incomplete development of photoresist layer 160. Polymer wall342 can function as a spring cantilever by itself or with a depositedlayer on it, and can also serve as a mold or form for production of aspring cantilever, as described below. The substantially planar sectionof the upper surface of wall 342 illustratively extends alongapproximately 75% of its length from substrate 104 to top surface 354.

FIG. 25 shows microstructure 370, with seed layer 372 and structure 374,respectively resembling seed layer 230 and structure 260 ofmicrostructure 270 in FIG. 17 but with its shape modified by rampsection 350. The spring cantilever of microstructure 370 includes curvedsection 376 with a curved shape resulting from and following thecurvature of ramp section 350. This curved shape distributes stress overa larger region than with an angular joint as in FIG. 17, greatlyreducing the risk of cracking between the first and second parts ofmicrostructure 370, even though curved section 376 deforms. Thesubstantially planar section of the lower surface of microstructure 370illustratively extends along approximately 60% or less of its lengthfrom substrate 104 to the free part or end.

Techniques as described above could be applied in various applications,including, in general, applications in which microstructures that arespring-like, resilient, elastic, or bendable are useful, such aspackaging and probing.

Some of the above exemplary implementations involve arrays ofmicrostructures, but the invention could be implemented with a singlemicrostructure, with or without a support structure. In addition, thetechniques described above in relation to FIGS. 1-25 can also be appliedto walls or wall-like structures that are larger than microstructures;in particular, the cross-sections of FIGS. 3, 4, 10-12, 16, 17, 21, and23-25 could be cross-sections of walls or wall-like structures. As usedherein, a “wall-like structure” is either a wall or a structure similarto a wall that does not fit the above definition of a wall because of aminor difference, such as that its thickness in places exceeds eitherits length or its width, or that, due to openings, gaps, orirregularities of some other sort, its length or width in places is lessthan its thickness, or that it is supported in such a way that it doesnot fit the above definition of a cantilevered element or the like.

FIG. 26 shows a pair of oblique wall-like structures 400 and 402 thatextend from their bases on support surface 404 of substrate 406 towardeach other. Structures 400 and 402 illustratively function as clips,holding tubular object 410 between their lower surfaces and supportsurface 404. Tubular object 410 could, for example, be an optical fiber(such as in an optical detection application for fluorescence orabsorption), a microfluidic capillary tube, or a conductive wire, forexample. In many such applications, precise alignment is required, suchas between an optical fiber and an on-chip device such as a laser, lens,or optical waveguide, and the technique of FIG. 26 may provide aprecise, low-cost approach.

Structures 400 and 402 can have widths and heights appropriate to thediameter of object 410 and to the spring force required to hold object410 in place after insertion without gluing or other additionalmeasures. As noted above, SU-8 can be produced with a height of up to 2mm under vertical exposure. Therefore, a 2 mm wall at an angle of 45°from a substrate could be processed from a 1.4 mm thick SU-8 layer.Thickness between a wall's upper and lower surfaces would depend onphotomask design, and typical thicknesses could be several microns totens of microns. More generally, a wall could be designed to besufficiently flexible for multiple insertions.

FIG. 27 shows a sequence of cross-sectional views along line 27-27′ inFIG. 26. Although the operations illustrated in FIG. 27 are appropriatefor producing a pair of walls or wall-like structures as in FIG. 26,they could also be performed to produce a pair of microstructuresadjacent to each other, or a microstructure paired with a wall orwall-like structure.

Cross-section 430 is very similar to FIG. 3, above, and the operationperformed can be understood from the description of FIG. 3 above.Photoresist layer 432 has been deposited on surface 404 of substrate406. Layer 432 can, for example, be SU-8, DiaPlate, or anotherphotoresist that can be used to produce relatively tall structures withhigh ratios of height to thickness. Layer 432 can have an appropriatethickness, such as between tens and a few thousands of microns. Maskingstructure 434 over layer 432 illustratively includes a single slot oropening through which light can be projected from a source onto layer432; masking structure 434 could include a rectangular opening likethose in mask portion 180 in FIG. 6, but much longer. As shown, light isreceived at the angle α₁ from the normal, and the resulting exposedportion of layer 432 will as a result extend at an oblique angle α₂ asdescribed in relation to FIG. 3, above.

In cross-section 440, masking structure 434 has been moved a distance ofΔx to the right relative to layer 432. Light is received at the angle α₃from the normal, where α₃ is approximately equal in magnitude butopposite in sign from α₁. The exposed portion of layer 432 willsimilarly extend at an oblique angle α₄ that is a function of α₃, and α₄will also be approximately equal in magnitude but opposite in sign fromα₂.

Cross-section 450 shows the structure obtained after development oflayer 432 and removal of nonexposed photoresist. As can be seen,structure 400 extends at the angle α₂ from the normal to surface 404,while structure 402 extends at the angle α₄ from the normal to surface404.

FIG. 28 illustrates another illumination technique that can be used toproduce structures similar to wall-like structures 400 and 402 in FIG.26. Rather than top-side illumination as in FIG. 27, the technique inFIG. 28 uses backside illumination. Transparent substrate 470 has asurface 472 on which mask 474 is formed with long rectangular openingsas described above. Mask 474 may be any suitable material deposited onsurface 472 and patterned to produce the rectangular openings.Photoresist layer 476 is then deposited over mask 474 as described abovein relation to FIG. 27.

During a first backside illumination, light is incident on the backsideof substrate 470 at the angle α₁ from the normal. Then, during a secondbackside exposure, light is incident on the backside of substrate 470 atthe angle α₂. The resulting exposed regions are therefore v-shaped withwall-like legs or wings extending toward each other.

FIG. 29 illustrates an actual array of v-shaped structures that has beenproduced using the technique illustrated in FIG. 28. The structuresshown in FIG. 29 were fabricated from a layer of SU-8 having a thicknessof approximately 0.15 mm on a glass substrate using backside exposure.FIG. 30 shows schematically how tubular objects could be insertedbetween adjacent v-shaped structures as shown in FIG. 29. A portion ofsubstrate 470 supports v-shaped structures 490, 492, and 494, which areparallel and adjacent in sequence. Optical fiber 500 is being insertedbetween structures 490 and 492 from the end, and capillary tube 502 issimilarly being inserted between structures 492 and 494 from the end.

Insertion of a tubular object between a pair of oblique walls orwall-like structures can be problematic. If the walls are closely spacedwith little separation, top insertion may be difficult, and endinsertion may be desirable. With structures as in FIG. 30, however,improper end insertion may cause delamination of the v-shaped structuresfrom the substrate.

FIG. 31 illustrates walls that are symmetrical but, in addition tospring-like portions, also include spreading portions that facilitateinsertion of a tubular object between the walls and the upper surface ofsubstrate 520. Each of structures 522 and 524 is an oblique wall-likestructure. Structures 522 and 524 could be produced using techniquessimilar to those described above in relation to FIGS. 27 and 28, butwith mask openings shaped so that each structure includes both aspring-like portion and a spreading portion between the spring-likeportion and an end to make insertion easier. Wall 522, for example,includes spring-like portion 530 and spreading portion 532, so that endportion 534 is a greater distance from structure 524 than portion 530is. Similarly, structure 524 includes spring-like portion 540, spreadingportion 542, and end portion 544, similarly a greater distance fromstructure 522 than portion 540 is. As a result, tubular object 550 canbe more easily inserted because the space at the opening between endportions 534 and 544 is relatively wide. Similarly, tubular object 550might be inserted from the top by a zipping action, with the part overend portions 534 and 544 inserted first and with the remainder insertedprogressively upward from the end opening through the spreading portions532 and 542 and then along the spring-like portions 530 and 540.

In general, wall-like structures as described above are especiallyappropriate for clipping or holding tubular objects, but objects of anyother appropriate shape could be inserted and held by such structures.Furthermore, any appropriate insertion technique could be used inaddition to those described above. Although additional measures such asglue or other attachment techniques could be used to hold an object morefirmly, in many applications the spring force of the structures will besufficient to hold an object in position. It may be beneficial, however,to provide additional positioning accuracy, using techniques asillustrated in FIG. 21, described above, and in FIGS. 32 and 33.

Although described above in relation to a microstructure implementation,the cross-section of FIG. 21 is also applicable to a wall or wall-likestructure that exceeds the size of a microstructure. In this case,object 302 can be laterally inserted from the right in FIG. 21, and isheld in place not only by the spring force of the wall or wall-likestructure, but also by the sidewalls of blocks 300 and 302 (or, if block300 is omitted, by the sidewall of block 302 alone). Sidewalls forprecise lateral alignment can be produced, for example, by patterning alayer of photoresist or metal on the substrate. Also, a v-groove orother similar groove may be etched into the substrate. In each of theseexamples, the oblique wall or walls serve primarily to provide springforce, pressing the object against the sidewalls or into the groove.Exact symmetry of the oblique walls or wall-like structures and theprecise angle become less important, because the sidewalls or grooveensure lateral stability despite differences in height or angle of theoblique structures.

In FIG. 32, wall-like structures 560 and 570 together hold object 304 inposition between the sidewalls of blocks 300 and 302. In FIG. 33, anadditional layer 580 of metal or other material has been coated ontostructures 560 and 570 as well as other exposed surfaces by a processsuch as sputtering, evaporation, or plating. Compared with FIG. 32, thestructures of FIG. 33 may be more rigid and less prone to fracture. Iflayer 580 is sufficiently resilient, photoresist could be removed, thusremoving structures 560 and 570 but leaving metal clips that could beused to hold an object and, if the object is an electrical wire, forexample, to provide a conductive path to other components.

FIG. 34, described with the same reference numerals as FIG. 21,illustrates an application in which object 304 is held in place againsta single sidewall of block 302. Wall-like structure 170 (which could bea microstructure) and alignment block 302 are each formed directly onsurface 104, positioned so that object 304 is held in place by thesidewall of block 302 after being laterally inserted from the right inFIG. 34. During insertion, object 304 applies deflecting force away fromsurface 104 to the lower surface of wall-like structure 170, but thedeflection is sufficient to allow insertion. After insertion, the springforce F is sufficient to hold object 304 in place.

In addition to sidewalls or a groove, other types of structures could beused to provide precise lateral alignment of an object held in place byoblique walls or wall-like structures. For example, the object could beheld in position against a vertical wall or against a series of posts.

FIG. 35 illustrates application of the structure shown in FIG. 32 for aparticularly promising application in microfluidics. In the illustratedexample, object 304 is a capillary tube pushed against microchannel 590,which could be fabricated from a photoresist such as SU-8. The sidewallsof blocks 300 and 302 are shown by dashed lines, and serve to holdobject 304 in lateral position. At the same time, structures 560 and 570act as clips, holding object 304 against blocks 300 and 302. Gasket 592at the end of the capillary tube acts as a sealant, and may beconstructed from silicone or other suitable material.

FIG. 36 shows another exemplary implementation that is similar to thatof FIG. 26, but with two rows of oblique cylinder-like microstructuresinstead of wall-like structures 400 and 402. The first row includesmicrostructures 600 and 602, and the second row includes microstructures610, 612, and 614. Each microstructure has uniformly oblique upper andlower surfaces, which can result from an oblique radiation process thatproduced it from a layer of polymer on surface 404 of substrate 406; theprocess can be similar to one of the processes described above inrelation to FIGS. 27 and 28. In addition, along each side between itsupper and lower surfaces, each microstructure can have a rounded sidesurface to facilitate insertion of object 410 from an end.Microstructures 600 and 610 are illustratively opposite each other,while microstructure 602 is illustratively offset but across frommicrostructures 612 and 614, another arrangement that can hold object410 between the lower surfaces of the microstructures and surface 404.In general, the microstructures could be in any suitable arrangement onopposite sides of the inserted position of object 410.

Some of the above exemplary implementations involve specific materials,such as photoresists and metals, but the invention could be implementedwith a wide variety of materials, including various substrates and othersupport structures, various polymer and photoresist materials, variousseed layers, and various plating materials. In particular, semiconductorand other metal and non-metal substrates could be used, and variousnon-metal plating materials could be used, such as polypyrrole and otherconductive polymers; ceramic coatings such as nickel-ceramic composites;and calcareous deposits. Also, magnetic metals and alloys could be usedsuch as plated Ni, CoNi, NiFe, FeCo, FeCoNi, etc., as described inAndricacos, P. C. and Robertson, N., “Future directions in electroplatedmaterials for thin film recording heads,” IBM Journal of Research andDevelopment, Vol. 42, No. 5, 1998, pp. 671-680. Also, layers of magneticand non-magnetic material could be plated. Furthermore, solder materialscould be plated such as PbSn, BiSn, or others.

The exemplary implementations generally include a structure with anoblique part, and the angle of obliqueness measured from the normalcould vary from a relatively small angle such as approximately 10°, justsufficient to ensure that an error will not produce a verticalstructure, to the largest angle achievable with the techniques beingused. An angle as great as approximately 70° may be achievable, such aswith exposure through a prism, as in FIG. 22. In general, smaller anglesallow denser packing of microstructures or wall-like structures, whilehigher angles provide cantilevered elements with better verticalcompliance. For specific implementations, these and other competingconstraints may mean that intermediate angles are advantageous, such as20°, 30°, 40°, 45°, or 60°.

Some of the exemplary implementations include uniformly obliquesurfaces, or sections of surfaces, resulting from oblique radiationtechniques. It is foreseeable, however, that other techniques will bedeveloped for producing uniformly oblique surfaces, and the invention isnot limited to uniformly oblique surfaces produced by oblique radiationtechniques.

Similarly, the above exemplary implementations suggest certaindimensions, but a wide range of dimensions would fall within the scopeof the invention, subject to relevant constraints. For example, some ofthe above embodiments include substantially planar parts that are muchthinner than the width and length of their surfaces, but thicker partswould also come within the scope of the invention.

In some of the exemplary implementations, a part of an electricallyconductive component of a microstructure or wall-like structure covers acontact, and, in general, a part of a microstructure or wall-likestructure could extend to other structures on a substrate, such as viacontacts, other microstructures or wall-like structures, through-wafervias, and so forth. Electrically conductive microstructures could beused for signal and power distribution. Thermally conductivemicrostructures or wall-like structures could be used for heatdistribution.

A few exemplary applications are described above, but many others couldbe identified. For example, microstructures and wall-like structures inaccordance with the invention could also serve simply as “springy”mechanical structures, e.g. as springy spacers in an assembly. Variousother clip applications are foreseeable, such as clipping an object inan anisotropically etched groove in a silicon substrate or with apolymeric alignment structure or electroplated groove. In addition, inthe clip applications, each wall-like structure might be replaced by aspring cantilever or by a series of spring cantilevers; in someapplications, two spring cantilevers opposite each other may suffice.

Exemplary implementations described above could be modified to providelateral compliance, such as by placing appropriate bends in amicrostructure's spring cantilever, such as in second part 114 of themicrostructure in FIG. 1.

Some exemplary implementations shown above have a tip on the free partor end of a microstructure, but the free part could simply terminate atan end and various other structures could be on the free part, includinga bump, a structure formed from a solderable material, or some othertype of structure.

The above exemplary implementations generally involve production ofmicrostructures and wall-like structures following particularoperations, but different operations could be performed, the order ofthe operations could be modified, some operations could be omitted, andadditional operations could be added within the scope of the invention.For example, radiation of any appropriate wavelength and intensity couldbe used in oblique radiation processes. Also, plating could be performedin many different ways, including various electroplating and electrolessplating techniques, and molds for plating an oblique part could beproduced in any appropriate way, including molding/embossing or laserablation. In addition, where contacts are present, they could beproduced at any appropriate stage in a sequence.

While the invention has been described in conjunction with specificexemplary implementations, it is evident to those skilled in the artthat many alternatives, modifications, and variations will be apparentin light of the foregoing description. Accordingly, the invention isintended to embrace all other such alternatives, modifications, andvariations that fall within the spirit and scope of the appended claims.

1. A method of use comprising: applying deflecting force to acantilevered element; the cantilevered element having a base supportedon a support surface, the cantilevered element extending from the baseto a free part; the cantilevered element including a spring-like portionthat, when undeflected, extends obliquely from the base to the freepart; the spring-like portion having an oblique radiation artifact,wherein applying the deflecting force involves inserting an objectbetween the cantilevered element and the support surface; and inresponse to deflecting force, providing deflection and spring forcewithin required ranges from the spring-like portion, and holding theobject between the cantilevered element and the support surface.
 2. Themethod of claim 1 wherein inserting the object under the cantileveredelement applies deflecting force away from the support surface; therequired ranges of deflection and spring force being such that, inresponse to deflecting force, the spring-like portion allows insertionof the object and holds the object between the spring-like portion andthe support surface after insertion of the object.
 3. The method ofclaim 1, wherein the artifact of the oblique radiation comprisesphotoresist.
 4. The method of claim 1, wherein the artifact of theoblique radiation comprises a polymer and the oblique radiation isoblique laser radiation.
 5. The method of claim 1, wherein thedeflecting force is applied to the spring-like portion in a directionhaving a component normal to the support surface and upward from thesupport surface that supports the base towards the spring-like portion.6. The method of claim 5, further comprising a block on the base,wherein the required ranges of the deflecting force are sufficient tohold an object between the base and the cantilevered element in contactwith the block and a lower surface of the cantilevered element.
 7. Themethod of claim 1, wherein: the cantilevered element is a firstcantilevered element and further comprising a second cantileveredelement that comprises a second artifact of oblique radiation thatextends obliquely from the base towards the first cantilevered element;and wherein the method further comprises holding an object between lowersurfaces of the first cantilevered element, the second cantileveredelement, and the base.
 8. The method of claim 1, wherein the artifact ofthe oblique radiation comprises one or more of photoresist, polymer, andmetal.
 9. A method of using an apparatus, the apparatus comprising: astructure with a support surface; and a cantilevered element fabricatedfrom material deposited over the support surface; the cantileveredelement having a base supported on the support surface and extendingfrom the base to a free part; the cantilevered element including: aflexible polymer component extending from the base to the free part;between the base and the free part, the polymer component including: aspring-like portion including an artifact of oblique radiation, thespring like portion, when undeflected, extends obliquely along a lengthbetween the base and the free part; and a surface that, along most ofthe spring-like portion's length, is uniformly oblique relative to thesupport surface; the spring-like portion being structured to respond todeflecting force applied to the cantilevered element in use by providingdeflection and spring force within required ranges; the methodcomprising: applying deflecting force to the cantilevered element; andin response to deflecting force, providing deflection and spring forcewithin required ranges from the spring-like portion, wherein the obliqueradiation is collimated radiation and the artifact of the obliqueradiation extends from the base at an angle α₂, wherein α₂ is related toan angle of the collimated oblique radiation, α₁.
 10. The method ofclaim 9 in which an object contacting the cantilevered element's freepart applies deflecting force toward the support surface; the requiredranges of deflection and spring force being such that, in response todeflecting force, the free part moves to a position responsive to theobject's position and the free part maintains contact with the object.11. The method of claim 9, wherein the material deposited over thesupport surface is deposited by one or more of sputter coating,evaporation, and electrodeposition.
 12. The method of claim 9, whereinafter deposition of the material, the material is patterned.
 13. Themethod of claim 9, wherein the cantilevered element is fabricated bydeposition and patterning of multiple layers of materials.
 14. Themethod of claim 9, wherein the oblique radiation comprises one or moreof collimated light, laser light, X-rays, and UV light.
 15. A method,comprising: applying a deflecting force to a cantilevered element, thecantilevered element formed of a layer of material deposited over asupport surface and having a base supported on the support surface, thecantilevered element comprising one or more of photoresist and polymerand extending from the base to a free part; the cantilevered elementincluding a spring-like portion that, when undeflected, extendsobliquely from the base to the free part; the spring-like portionincluding an artifact of collimated oblique radiation; and in responseto deflecting force, providing deflection and spring force withinrequired ranges from the spring-like portion.
 16. The method of claim15, wherein the collimated oblique radiation is one or more of UV lightand X-rays.
 17. The method of claim 15, wherein the oblique radiationcomprises laser radiation.